Alteration of earlier nither, from Middle English nitheren, from Old English niþerian (" to depress, abase, bring low, humiliate, oppress, accuse, condemn"), from Old English niþer ("below, beneath, down, downwards, lower, in an inferior position"). See above. (Wiktionary)

Examples

So, if you wouldn't mind, please supply a source for that figure, or will ASSume it came from a thin nether region!

Old Solomon, in his seedy clothes and long white locks, seemed to be luring that decent company by the magic scream of his fiddle -- luring discreet matrons in turban shaped caps, nay, Mrs. Crackenthorp herself, the summit of whose perpendicular feather was on a level with the Squire's shoulder -- luring fair lasses complacently conscious of very short waists and skirts blameless of front - folds -- luring burly fathers in large variegated waist-coats, and ruddy sons, for the most part shy and sheepish, in short nether garments and very long coat-tails.

Solomon, in his seedy clothes and long white locks, seemed to be luring that decent company by the magic scream of his fiddle -- luring discreet matrons in turban-shaped caps, nay, Mrs. Crackenthorp herself, the summit of whose perpendicular feather was on a level with the Squire's shoulder -- luring fair lasses complacently conscious of very short waists and skirts blameless of front-folds -- luring burly fathers in large variegated waistcoats, and ruddy sons, for the most part shy and sheepish, in short nether garments and very long coat-tails.

JANET RENO, U.S. ATTORNEY GENERAL: Everyday that goes by in which Elian is not reunited with his father and this matter brought to a conclusion is -- can be disruptive and no child should be in that kind of nether-nether land for that long.

In the following paragraphs, I have drawn freely from materials in Sornig's book -- but for my own purposes in this article: the book itself uses the examples to illustrate a variety of sources of slang in accordance with the author's analysis of the "nether" reaches of the language, an analysis I shall only touch on here and there.